In both groups, marked improvements in sleep metrics were observed (Table 5) and UACR decreased significantly after CPAP treatment, although this decrease was more marked in the severe OSA with high periostin group than that in the severe OSA alone group (− 71.4 ± 186.2 mg/g vs. − 12.9 ± 63.1 mg/g, p = 0.04). Here, POSTN is linked to obstructive sleep apnea syndrome.